By Dominic Casciani
BBC News at the National Archives
Whatever you do, don't forget your smart luggage - and never, ever meet in smart West End hotels.
Public transport: Good for a rendezvous
That was the top secret advice to would-be communist spies in a previously unseen handbook on surviving in 1930s London.
The alternative tourist guide to London, compiled to aid infiltration into the UK, has been revealed amid hundreds of MI5 documents published at the National Archives.
But the guide also reveals what could be the first concrete link between London and one of the Soviet Union's master spies during the World War II: the head of the "Red Orchestra" anti-Nazi network.
According to the documents, the guide emerged when the Germans initially seized papers from Soviet agents during the war. When the Germans were themselves in retreat, the guide somehow fell into the hands of MI5.
The guide, a kind of Time Out of its era without the shopping recommendations, lists what to do in London, including the best places to meet without blowing your cover.
"The West End with its nightlife, the big hotels with foreign statesmen and jewellery-wearing society ladies all these make central London the most closely policed area of England," writes the anonymous author.
"There are no reasons why one should not use the hotels in this area - but it is remarkable how persistently this area is preferred for rendezvous by people who should know better.
"There is no reason why one should not live [in South Kensington] but rendezvous in the outlying districts of Greater London," the spy comments.
"Thus one can pass both on the way to the rendezvous and on the homeward journey through the central area with all its stores, museums shops, subways etc (having several entrances) in order to make sure one is not shadowed."
The key was to use large stores, such as Liberty on Regent Street, to quickly lose a tail by dodging in and out of the various departments.
Suggested central London meeting places included Trafalgar Square's subway tunnels and the Peter Pan Statue in Kensington Gardens.
However, the writer preferred outlying locations such as the Kew Gardens, Richmond Park, North Harrow's Embassy Cinema, Pinner Underground Station booking hall and, strangest of them all, the Number 83 bus stop in Wembley, direction Ealing.
A definite benefit was AA membership (£2, two shillings a year) because the club guaranteed free legal representation in the courts if it was ever needed in relation to a traffic accident.
This was not communist Russia penny pinching - rather a cunning attempt to minimise any kind of contact with the authorities.
Keep an eye out for this bloke
Hotels were however tricky places to meet. Some such as the Dorchester and Ritz required the "necessary social standing". Others could consider you suspicious if you acted differently.
"It is advisable to arrive at all hotels with smart and sufficient luggage. The British spend a lot of money on good luggage and travellers risk being turned away or asked for a deposit if they do not comply with this custom," says the author.
So who wrote the guide? That we don't know - but an unnamed MI5 analyst left some clues.
"It is possible that the document should be linked to Red Army intelligence interests," says the agent's comments on the papers.
"Trepper visited the UK five or six times between 1937 and 1939, his last visit being probably in the summer of 1939 for the purpose of discussing the possibilities of a Red Army Intelligence network."
Leopold Trepper was one of the best and most highly decorated Soviet spies. A Polish Jew, he escaped to Moscow at the start of the war and was recruited by the NKVD, a branch of Soviet Union's secret police.
He established a network of communist agents, "Die rote Kapelle", the Red Orchestra. It sought to undermine the Nazis in western Europe and got so good he may have tapped Nazi phones in France prior to his capture and interrogation.
Trepper returned to Moscow at the end of the war - but was swept up in Stalin's paranoid purges - the leadership convinced he was now a threat. He escaped with his life thanks to friends in high places - and after 10 years in jail left for Poland.
He later retired to Israel and completed his memoirs of the war before his death in 1982.